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Donor Impurity-Related Optical Absorption in GaAs Elliptic-Shaped Quantum Dots
(HINDAWI LTD, 2017) Londono, M. A.; Restrepo, R. L.; Ojeda, J. H.; Huynh Vinh Phuc; Mora-Ramos, M. E.; Kasapoglu, E.; Morales, A. L.; Duque, C. A.
The conduction band and electron-donor impurity states in elliptic-shaped GaAs quantum dots under the effect of an externally applied electric field are calculated within the effective mass and adiabatic approximations using two different numerical approaches: a spectral scheme and the finite element method. The resulting energies and wave functions become the basic information needed to evaluate the interstate optical absorption in the system, which is reported as a function of the geometry, the electric field strength, and the temperature.
Effects of electric and magnetic fields on the electronic properties in the asymmetrical biconvex lens-shaped GaAs/GaAlAs quantum dots
(Elsevier, 2024) Al, E. B.; Restrepo, R. L.; Morales, A. L.; Mora-Rey, F.; Sosa-Giraldo, T.
Theoretical investigation of electronic properties in asymmetric biconvex lens -shaped GaAs/GaAlAs quantum dots is considered in the presence of the external magnetic and electric fields. In addition, the effects of the dot size and the asymmetry of the structure on the electronic properties are also investigated. The shape of this quantum dot corresponds to the intersection of two differently centered spheres. The energy levels and wave functions of the shallow hydrogenic impurity in the structure with a finite potential are calculated numerically in cylindrical coordinates with the effective mass approach using a complex eigenvalue formalism through a two-dimensional axisymmetrical and three-dimensional finite element methods. The results reveal significant dependence of the calculated physical properties on lens dimensions, axial impurity position, and intensities of applied electric and magnetic fields.
Effects of Geometry on the Electronic Properties of Semiconductor Elliptical Quantum Rings
(NATURE PUBLISHING GROUP, 2018) Vinasco, J. A.; Radu, A.; Kasapoglu, E.; Restrepo, R. L.; Morales, A. L.; Feddi, E.; Mora-Ramos, M. E.; Duque, C. A.
The electronic states in GaAs-AlxGa1-xAs elliptically-shaped quantum rings are theoretically investigated through the numerical solution of the effective mass band equation via the finite element method. The results are obtained for different sizes and geometries, including the possibility of a number of hill-shaped deformations that play the role of either connected or isolated quantum dots (hills), depending on the configuration chosen. The quantum ring transversal section is assumed to exhibit three different geometrical symmetries - squared, triangular and parabolic. The behavior of the allowed confined states as functions of the cross-section shape, the ring dimensions, and the number of hills-like structures are discussed in detail. The effective energy bandgap (photoluminescence peak with electron-hole correlation) is reported as well, as a function of the Al molar fraction.
The effects of intense laser field and applied electric and magnetic fields on optical properties of an asymmetric quantum well
(ELSEVIER SCIENCE BV, 2015) Restrepo, R. L.; Ungan, F.; Kasapoglu, E.; Mora-Ramos, M. E.; Morales, A. L.; Duque, C. A.
This paper presents the results of the theoretical study of the effects of non resonant intense laser field and electric and magnetic fields on the optical properties (the linear and third order nonlinear refractive index and absorption coefficients) in an asymmetric quantum well. The electric field and intense laser field are applied along the growth direction of the asymmetric quantum well and the magnetic field is oriented perpendicularly. To calculate the energy and the wave functions of the electron in the asymmetric quantum well, the effective mass approximation and the method of envelope wave function are used. The asymmetric quantum well is constructed by using different aluminium concentrations in both right and left barriers. The confinement in the quantum well is changed drastically by either the effect of electric and magnetic fields or by the application of intense laser field. The optical properties are calculated using the compact density matrix approach. The results show that the effect of the intense laser field competes with the effects of the electric and magnetic fields. Consequently, peak position shifts to lower photon energies due to the effect of the intense laser field and it shifts to higher photon energies by the effects of electric and magnetic fields. In general, it is found that the concentration of aluminum, electric and magnetic fields and intense laser field are external agents that modify the optical responses in the asymmetric quantum well. (C) 2014 Elsevier B.V. All tights reserved.
Electron Raman scattering in a double quantum well tuned by an external nonresonant intense laser field
(ELSEVIER SCIENCE BV, 2017) Tiutiunnyk, A.; Mora-Ramos, M. E.; Morales, A. L.; Duque, C. M.; Restrepo, R. L.; Ungan, F.; Martinez-Orozco, J. C.; Kasapoglu, E.; Duque, C. A.
In this work we shall present a study of inelastic light scattering involving inter-subband electron transitions in coupled GaAs-(Ga,AI)As quantum wells. Calculations include the electron related Raman differential cross section and Raman gain. The effects of an external nonresonant intense laser field are used in order to tune these output properties. The confined electron states will be described by means of a diagonalization procedure within the effective mass and parabolic band approximations. It is shown that the application of the intense laser field can produce values of the intersubband electron Raman gain above 400 cm(-1). The system proposed here is an alternative choice for the development of Al chi Ga1-chi As semiconductor laser diodes that can be tuned via an external nonresonant intense laser field. (C) 2017 Elsevier B.V. All rights reserved.
Electronic states in GaAs-(Al, Ga) As eccentric quantum rings under nonresonant intense laser and magnetic fields
(NATURE PUBLISHING GROUP, 2019) Vinasco, J. A.; Radu, A.; Niculescu, E.; Mora-Ramos, E.; Feddi, E.; Tulupenko, V.; Restrepo, R. L.; Kasapoglu, E.; Morales, A. L.; Duque, C. A.
The features of the electron energy spectrum in eccentric two-dimensional GaAs-AlGaAs quantum rings of circular shape are theoretically investigated taking into account the effect of externally applied magnetic and intense laser fields. Analytical expressions for the laser-dressed confining potential in this kind of quantum ring geometry are reported for the first time. Finite element method is used to solve the resulting single-particle effective mass two-dimensional partial differential equation. It is shown that the allowed level spectrum is greatly influence by the external probe as well as by the breaking of geometric symmetry related to the changes in eccentricity. In presence of an intense laser field, the conduction band confining profile suffers strong modifications along the structure, with an additional contribution to symmetry breaking. These modifications of electronic quantum states reflect in the intraband optical absorption. Accordingly, the features of the intraband transitions are discussed in detail, revealing the significant influence of the magnetic field strength and laser field intensity and polarization, together with eccentricity, in the allowing of ground-to-excited states transitions and their corresponding intensities.
Electronic structure and optical properties of triangular GaAs/AlGaAs quantum dots: Exciton and impurity states
(ELSEVIER SCIENCE BV, 2016) Tiutiunnyk, A.; Akimov, V.; Tulupenko, V.; Mora-Ramos, M. E.; Kasapoglu, E.; Ungan, F.; Sokmen, I.; Morales, A. L.; Duque, C. A.
Electronic structure and optical properties in equilateral triangular GaAs/Al0.3Ga0.7As quantum dots are studied extensively. The effects of donor and acceptor impurity atoms positioned in the orthocenter of the triangle, as well as of the external DC electric field are taken into account. Binding energies of the impurity, exciton energies, interband photoluminescence peak positions as well as linear and non-linear optical properties in THz range caused by transitions between excitonic states are calculated and discussed. (C) 2015 Elsevier B.V. All rights reserved.
Intense laser field effects on a Woods-Saxon potential quantum well
(ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2015) Restrepo, R. L.; Morales, A. L.; Akimov, V.; Tulupenko, V.; Kasapoglu, E.; Ungan, F.; Duque, C. A.
This paper presents the results of the theoretical study of the effects of non-resonant intense laser field and electric and magnetic fields on the optical properties in an quantum well (QW) make with Woods Saxon potential profile. The electric field and intense laser field are applied along the growth direction of the Woods Saxon quantum well and the magnetic field is oriented perpendicularly. To calculate the energy and the wave functions of the electron in the Woods Saxon quantum well, the effective mass approximation and the method of envelope wave function are used. The confinement in the Woods Saxon quantum well is changed drastically by the application of intense laser field or either the effect of electric and magnetic fields. The optical properties are calculated using the compact density matrix. (C) 2015 Elsevier Ltd. All rights reserved.
Intersubband optical absorption coefficients and refractive index changes in a graded quantum well under intense laser field: Effects of hydrostatic pressure, temperature and electric field
(ELSEVIER SCIENCE BV, 2014) Ungan, F.; Restrepo, R. L.; Mora-Ramos, M. E.; Morales, A. L.; Duque, C. A.
The effects of hydrostatic pressure, temperature, and electric field on the optical absorption coefficients and refractive index changes associated with intersubband transition in a typical GaAs/Ga0.7Al0.3As graded quantum well under intense laser field have been investigated theoretically. The electron energy eigenvalues and the corresponding eigenfunctions of the graded quantum well are calculated within the effective mass approximation and envelope wave function approach. The analytical expressions of the optical properties are obtained using the compact density-matrix approach and the iterative method. The numerical results show that the linear and nonlinear optical properties depend strongly on the intense laser field and electric field but weakly on the hydrostatic pressure and temperature. Additionally, it has been found that the electronic and optical properties in a GaAs/Ga0.7Al0.3As graded quantum well under the intense laser field can be tuned by changing these external inputs. Thus, these results give a new degree of freedom in the devices applications. (C) 2013 Elsevier B.V. All rights reserved.
Linear and nonlinear optical properties in the terahertz regime for multiple-step quantum wells under intense laser field: Electric and magnetic field effects
(ELSEVIER SCIENCE BV, 2018) Restrepo, R. L.; Gonzalez-Pereira, J. P.; Kasapoglu, E.; Morales, A. L.; Duque, C. A.
We present a theoretical study on the linear and nonlinear optical properties in AlrGa1-rAs/GaAs asymmetric multiple step quantum wells (AMSQW) under the effects of a non-resonant intense laser field (ILF), electric, and magnetic field. Calculations are for the linear optical absorption and refractive index relative changes combined with the second and third harmonic generation. The potential profile is constructed as a function of the Aluminum concentration, so that the heterostructure has four steps of different concentration, width and height. The energy levels and corresponding wavefunctions are obtained by solving the Schordinger equation, for an electron, in the envelope function approach, with parabolic bands, and the effective mass approximations. The results show that variations in ILF, electric field and magnetic field have significant influences on the magnitude and peak energy positions of the SHG and THG coefficients. Therefore, we can conclude that the effects of ILF, electric and magnetic fields can be used to tune and control the SHG and THG in the range of the terahertz electromagnetic spectrurn.
Optical coefficients in a semiconductor quantum ring: Electric field and donor impurity effects
(ELSEVIER SCIENCE BV, 2016) Duque, C. M.; Acosta, Ruben E.; Morales, A. L.; Mora-Ramos, M. E.; Restrepo, R. L.; Ojeda, J. H.; Kasapoglu, E.; Duque, C. A.
The electron states in a two-dimensional quantum dot ring are calculated in the presence of a donor impurity atom under the effective mass and parabolic band approximations. The effect of an externally applied electric field is also taken into account. The wavefunctions are obtained via the exact diagonalization of the problem Hamiltonian using a 2D expansion within the adiabatic approximation. The impurity-related optical response is analyzed via the optical absorption, relative refractive index change and the second harmonics generation. The dependencies of the electron states and these optical co-efficients with the changes in the configuration of the quantum ring system are discussed in detail. (C) 2016 Elsevier B.V. All rights reserved.
Second and third harmonic generation associated to infrared transitions in a Morse quantum well under applied electric and magnetic fields
(ELSEVIER SCIENCE BV, 2017) Restrepo, R. L.; Kasapoglu, E.; Sakiroglu, S.; Ungan, F.; Morales, A. L.; Duque, C. A.
The effects of electric and magnetic fields on the second and third harmonic generation coefficients in a Morse potential quantum well are theoretically studied. The energy levels and corresponding wave functions are obtained by solving the Schrodinger equation for the electron in the parabolic band scheme and effective mass approximations and the envelope function approach. The results show that both the electric and the magnetic fields have significant influence on the magnitudes and resonant peak energy positions of the second and third harmonic generation responses. In general, the Morse potential profile becomes wider and shallower as gamma-parameter increases and so the energies of the bound states will be functions of this parameter. Therefore, we can conclude that the effects of the electric and magnetic fields can be used to tune and control the optical properties of interest in the range of the infrared electromagnetic spectrum. (C) 2017 Elsevier B.V. All rights reserved.
Theoretical study of electronic and optical properties in doped quantum structures with Razavy confining potential: effects of external fields
(Springer, 2022) Dakhlaoui, Hassen; Gil-Corrales, J. A.; Morales, A. L.; Kasapoglu, E.; Radu, A.; Restrepo, R. L.; Tulupenko, V
We investigate the energy states of confined electrons in doped quantum structures with Razavy-like confining potentials. The theoretical investigation is performed within the effective mass and parabolic band approximations, including the influence of externally applied electric and magnetic fields. First, we analyze the case of a Razavy quantum well and determine its conduction subband spectrum, focusing on the lowest energy levels and their probability densities. These properties have been numerically determined by self-consistently solving the coupled system of Schrodinger, Poisson, and charge neutrality equations. Doping is introduced via an on-center delta-like layer. In order to evaluate the associated total (linear plus nonlinear) optical absorption coefficient (TOAC), we have calculated the corresponding diagonal and off-diagonal electric dipole matrix elements, the main energy separation, and the occupancy ratio which are the main factors governing the variation in this optical response. A detailed discussion is given about the influence of doping concentration as well as electric and magnetic fields, which can produce shifts in the light absorption signal, toward either lower or higher frequencies. As an extension of the self-consistent method to a two-dimensional problem, the energy states of quantum wire system of circular cross section, with internal doping and Razavy potential, have been calculated. The response of eigenvalues, self-consistent potentials and electron densities is studied with the variation in delta-doping layer width and of the donor density. Finally, the origin of Friedel-like oscillations, that arise in the density profile, generated by the occupation of internal and surface electronic states has been explained.

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